-----Original Message-----
From: Thomas Zimmermann [mailto:tzimmerm...@suse.de]
Sent: Monday, September 20, 2021 4:17 PM
To: Kuo-Hsiang Chou <kuohsiang_c...@aspeedtech.com>;
dri-devel@lists.freedesktop.org; linux-ker...@vger.kernel.org
Subject: Re: [PATCH] drm/ast: Atomic CR/SR reg R/W
Hi
Am 17.09.21 um 09:22 schrieb KuoHsiang Chou:
> 1. Avoid IO-index racing
> 2. IO-index racing happened on resolustion switching
> and mouse moving at the same time
> 3. System hung while IO-index racing occurred.
I'd say that there's something else going one here. Mode setting and cursor
movement should be protected against each other by DRM locking.
Changing these low-level functions would not solve the issues. I'll try to
reproduce the problem ASAP.
Hi Thomas,
Sorry to interrupt you again!
May I understand the review's situation? Thanks!
Best Regards,
Kuo-Hsiang Chou
Best regards
Thomas
>
> Signed-off-by: KuoHsiang Chou <kuohsiang_c...@aspeedtech.com>
> ---
> drivers/gpu/drm/ast/ast_main.c | 48 +++++++++++++++++++++++++---------
> 1 file changed, 36 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/gpu/drm/ast/ast_main.c
> b/drivers/gpu/drm/ast/ast_main.c index 79a361867..1d8fa70c5 100644
> --- a/drivers/gpu/drm/ast/ast_main.c
> +++ b/drivers/gpu/drm/ast/ast_main.c
> @@ -41,28 +41,52 @@ void ast_set_index_reg_mask(struct ast_private *ast,
> uint32_t base, uint8_t index,
> uint8_t mask, uint8_t val)
> {
> - u8 tmp;
> - ast_io_write8(ast, base, index);
> - tmp = (ast_io_read8(ast, base + 1) & mask) | val;
> - ast_set_index_reg(ast, base, index, tmp);
> + uint16_t volatile usData;
> + uint8_t volatile jData;
> +
> + do {
> + ast_io_write8(ast, base, index);
> + usData = ast_io_read16(ast, base);
> + } while ((uint8_t)(usData) != index);
> +
> + jData = (uint8_t)(usData >> 8);
> + jData &= mask;
> + jData |= val;
> + usData = ((uint16_t) jData << 8) | (uint16_t) index;
> + ast_io_write16(ast, base, usData);
> }
>
> uint8_t ast_get_index_reg(struct ast_private *ast,
> uint32_t base, uint8_t index)
> {
> - uint8_t ret;
> - ast_io_write8(ast, base, index);
> - ret = ast_io_read8(ast, base + 1);
> - return ret;
> + uint16_t volatile usData;
> + uint8_t volatile jData;
> +
> + do {
> + ast_io_write8(ast, base, index);
> + usData = ast_io_read16(ast, base);
> + } while ((uint8_t)(usData) != index);
> +
> + jData = (uint8_t)(usData >> 8);
> +
> + return jData;
> }
>
> uint8_t ast_get_index_reg_mask(struct ast_private *ast,
> uint32_t base, uint8_t index, uint8_t mask)
> {
> - uint8_t ret;
> - ast_io_write8(ast, base, index);
> - ret = ast_io_read8(ast, base + 1) & mask;
> - return ret;
> + uint16_t volatile usData;
> + uint8_t volatile jData;
> +
> + do {
> + ast_io_write8(ast, base, index);
> + usData = ast_io_read16(ast, base);
> + } while ((uint8_t)(usData) != index);
> +
> + jData = (uint8_t)(usData >> 8);
> + jData &= mask;
> +
> + return jData;
> }
>
> static void ast_detect_config_mode(struct drm_device *dev, u32
> *scu_rev)
> --
> 2.18.4
>
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Felix Imendörffer
